Summer is nesting season for Rockies’ birdlife
by
Ward Cameron
Now is the time of year in the Canadian Rockies when we begin to see young birds making their first appearance. Over the past month I've been lucky to photograph calliope hummingbirds, osprey, great-blue heron and great-horned owls on the nest. The nesting instinct is one of the strongest instincts in most birds and can tell us a lot about each individual species.
Generally, the breeding cycle is an annual affair; however there are often two or even three occasions when eggs may be laid. In poor conditions, nesting may be omitted all together. For instance snowy owls, which breed in the north, can lay up to seven eggs during periods of plentiful food, but may not nest at all during lean years.
Normally, breeding takes place at the most opportune time as far as climate and availability of food are concerned. In most climates, including our own, this is in the spring. Since southern climes seem to feel the warmth of spring much earlier than more northerly areas, birds tend to breed earlier as well. Near the equator, where the length of day and temperature vary little over the course of the year, birds do not necessarily follow the same breeding schedule. Some simply maintain a rhythm of one to three broods per year.
Nests are often mistakenly referred to as bird's homes; however they are more akin to cradles in which they raise their young. Birds only have a nest when they have eggs or young that need their care. Generally birds only use nests for a short period during the year. For most birds, the majority of the year has only two requirements: food and protection. They do not have any connections with the opposite sex at times other than the mating season. This may not be too surprising, but it also brings to light another fact: singing is largely related to mating and nesting and as a result, during the winter months most birds sing very little.
A great-horned owl on its nest is a rare sight indeed, as these birds are elusive.
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A calliope hummingbird attends to its summer nest in its mountain home.
Generally, the males arrive back from migration first and in most cases they are the ones to choose the general location in which nesting will occur. The male will begin to sing loudly to both attract potential mates and repel other males from his territory. With the selection of a mate, the singing ends and the nesting begins.
In most cases the female does most of the nest building and brooding. More often than not, the eggs are laid at a rate of one per day until the entire complement has been laid. The actual care given to the young depends upon the species. Some birds, like grouse, are able to leave the nest within a very short time after hatching and therefore require little care. Others, like songbirds, are completely dependent upon their parents for quite some time after hatching. Eventually, the nestlings take their first flight and this also marks the beginning of independence for most birds. This may be a reluctant independence and often the parent birds will swallow an insect in direct view of the begging young, presumably in order to show them that it's time to fend for themselves.
With the end of the nesting season, the parent birds generally part company and for the remainder of the year will have little or no connection with one another – and then it all begins again.
Ward Cameron is a Canmore-based naturalist, photographer and author. His website, www.mountainnature.com, is an on-line guide to the nature of the Rocky Mountains. His popular guide book, Canmore & Kananaskis: Best Hikes, Best Activities , includes hiking trails, popular attractions, historical vignettes and superb colour photography.
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